The high-pressure fuel pump at which the present invention aims is provided with a plunger which is slidably fitted to a cylinder, and one end of the plunger reciprocates within a pressurizing chamber, thereby compressing and pressurizing a fuel introduced to the pressurizing chamber from an intake valve mechanism so as to discharge from a discharge valve mechanism. The plunger is achieved by converting a rotating motion of a cam which is formed in a cam shaft of the engine into an upward and downward reciprocating motion of the plunger. An annular retainer in which a lower end of the plunger is fixed to a center portion is stored within a tappet on a cup, and a roller is attached to a surface of the tappet in an opposite side to the retainer, and the roller is brought into pressure contact with the cam, and moves up and down along the surface of the cam in accordance with the rotation of the cam, thereby moving up and down the plunger. A helical spring is installed between the retainer and the pump housing (or the cylinder) in such a manner as to surround the plunger, and the spring is compressed on the basis of the rotation of the cam at a time of an ascending step of the plunger. In a descending step of the plunger, the plunger moves down along the cam surface on the basis of a compression reaction force of the spring. (the roller is not necessarily required.)
In this case, this kind of high-pressure pump has a narrow portion in which a diameter becomes smaller than a diameter of a sliding portion of the plunger with the cylinder, in a portion (a portion surrounded by the spring) of a lower end portion of the plunger, and a step portion (a neck portion) is formed in a diameter switch portion.
The lower end portion of the plunger is pressure inserted and fixed to a retainer having a through hole in the center in accordance with a close fit (International Laid-Open Pamphlet WO2006/069819).
An end portion in a side of the retainer of the plunger protrudes slightly out of the lower end surface of the retainer, a protruding portion comes into contact with a surface of the tappet, and an annular surface in a side of the tappet of the annular retainer faces to a surface in a side of the retainer of the tappet while keeping a necessary gap. The necessary gap is a distance which is larger than a swing range of the tappet at a time when the tappet swings on the basis of the rotation of the cam.